My daughter in law has a 4 cyl 1993 Magna auto sedan which she has just spent $2500 + on repairs after it overheated and cracked the head.

Since she got it back from the mechanic she will be driving along and it will just shut down - no power whatsoever. Her mechanic has had it back 10 times. He changed the disi, coil, and just about everything else but it keeps shutting down, after short run / long run / hot day / cold day etc. Eventually it will start again and might run for another week. No one seems to know what the problem is. Any clues????

when you say shut down and no power, do you mean the engine switches off, or the engine keeps running but it just free-revs when you hit the throttle?

It just switches off - no electrics whatsoever

If you're able to start it without a jump or new battery then you can rule out a bad alternator or battery.

It could be a faulty ECU causing the system to shut itself off (this is the only other thing that governs all electronics in the system. However the ECU could also be working fine and getting a bad code from a sensor thats telling it to shut down.

Ask the mechanic if he has an OBD-I (one not the letter i) scanner to assess if its getting any codes that could lead you in the right direction. If he doesnt then i suggest finding a mechanic that does. Or you could find the procedure to retrieve these codes yourself with a volt tester. I can tell you how to do this and how to read/interpret it all on a Diamante but i'm sure its different on a Magna so maybe someone else can chime in and let you know.

its possible it could be the ECU, something inside (cant remember what) burns out causing electrical problems,

its seems to be a common problem on 2nd gen 4cyl,

could be a loose wire, maybe just in contact by luck :confused:

my TN was doing this quite alot it ended up been the positive battery terminal as it is a plastic molded terminal the battery acid eats the metal out of it causing bad contact and droping the voltage well below usable levels when a large load is put on it.

Thanks - that should give me a bit to go on.